Shpakov A O, Gur'ianov I A, Vorob'ev V I, Avdeeva E V, Kuznetsova L A, Plesneva S A, Chubeĭ N M, Pertseva M N, Vlasov G P
I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry RAS.
Tsitologiia. 2004;46(3):268-76.
The coupling of hormone-activated receptor and heterotrimeric G protein is an important step of the signal transduction through adenylyl cyclase signal system (ACS). The numerous literature data and own results show that G protein-interacting regions, that are localized in cytoplasmic loops of receptors, have considerable positive charge, can form amphiphilic alpha-helices and are tightly associated with the membrane. We studied the influence of model cationic peptides on both basal and stimulated by hormones and nonhormonal agents adenylyl cyclase (AC) activity and on GTP binding activity of heterotrimeric G proteins in skeletal muscles of rats and smooth muscles of mollusc Anodonta cygnea. Peptides with hydrophobic radicals of caprinoyl acid (C10): Lys(C10)-His-Glu-Lys-Lys-(C10)-His-Glu-Lys-Lys(C10)-His-Glu-Lys-Lys(C10)- His-Glu-Lys-Ala-amide (peptide I), Cys-Lys(C10)-X-Tyr-Lys-Ala-Lys7-Trp-Lys-amide (II), Cys-X-Trp-Lys-Lys(C10)-Lys2-Lys(C10)-Lys3-Lys(C10)-Tyr-Lys-Lys(C10)-Lys-Lys- amide (III), where X--epsilon-aminocaproyl acid residue, were synthesized by solid-phase methodology. IC50 values for inhibiting the influence of peptides on serotonin-(molluscs) and isoproterenol-stimulated (rats) AC activity were: for peptide I--56 and 70 mkM, for peptide II--32 and 47 mkM, for peptide III--22 and 28 mkM, respectively. At the same time the peptides weakly decreased AC activity stimulated by nonhormonal agents (NaF, Gpp[NH]p, forskolin). Peptides I--III stimulated basal activity of the enzyme in both investigated tissues. The maximum stimulating effects (28--52%) of the peptides were observed at their concentration 10 mkM. Peptides (10--100 mkM) increased Gpp[NH]p binding in plasma membranes of mollusc and rat muscles and strongly decreased the influence of the hormones on the binding. Based on the obtained data we supposed that cationic peptides with hydrophobic radicals mimic G protein-binding regions of the receptors and can be involved in the regulation of functional coupling between the receptors and G proteins.
激素激活受体与异源三聚体G蛋白的偶联是通过腺苷酸环化酶信号系统（ACS）进行信号转导的重要步骤。众多文献数据及我们自己的研究结果表明，位于受体胞质环中的G蛋白相互作用区域带有大量正电荷，可形成两亲性α螺旋，且与膜紧密相连。我们研究了模型阳离子肽对大鼠骨骼肌和软体动物天鹅绒蛞蝓平滑肌中基础状态下以及受激素和非激素因子刺激后的腺苷酸环化酶（AC）活性，以及对异源三聚体G蛋白GTP结合活性的影响。合成了带有癸酰基酸（C10）疏水基团的肽：Lys（C10）-His-Glu-Lys-Lys-（C10）-His-Glu-Lys-Lys（C10）-His-Glu-Lys-Lys（C10）-His-Glu-Lys-Ala-酰胺（肽I）、Cys-Lys（C10）-X-Tyr-Lys-Ala-Lys7-Trp-Lys-酰胺（II）、Cys-X-Trp-Lys-Lys（C10）-Lys2-Lys（C10）-Lys3-Lys（C10）-Tyr-Lys-Lys（C10）-Lys-Lys-酰胺（III），其中X为ε-氨基己酸残基，采用固相方法合成。肽对5-羟色胺（软体动物）和异丙肾上腺素刺激（大鼠）的AC活性抑制作用的IC50值分别为：肽I为56和70μM，肽II为32和47μM，肽III为22和28μM。同时，这些肽对非激素因子（NaF、Gpp[NH]p、福斯可林）刺激的AC活性有微弱降低作用。肽I - III在两种研究组织中均刺激了该酶的基础活性。在肽浓度为10μM时观察到最大刺激作用（28 - 52%）。肽（10 - 100μM）增加了软体动物和大鼠肌肉质膜中Gpp[NH]p的结合，并强烈降低了激素对结合的影响。基于所获数据，我们推测带有疏水基团的阳离子肽模拟了受体的G蛋白结合区域，并可能参与受体与G蛋白之间功能偶联的调节。
